The present disclosure relates to methods for forming a zinc alloy powder as a negative electrode active material of an alkaline battery.
In general, zinc powders as a negative electrode active material of an alkaline battery are alloyed with other metals in view of corrosion resistance. For example, zinc alloy powders with an increased resistance to corrosion which are obtained by adding a metal with a high hydrogen overvoltage, such as indium and bismuth, or adding a metal which can make the powders have smooth surfaces, such as aluminum and calcium, are known.
Many alkaline batteries currently on the market use a zinc alloy powder which contains 0.01-0.1% indium and bismuth by mass and 0.002-0.01% aluminum by mass.
The zinc alloy powder for use in the alkaline batteries may be obtained from a zinc alloy molten metal obtained by mixing and melting metals, i.e., indium, bismuth and aluminum, and zinc (see Japanese Unexamined Patent Publication No. 2006-40883).
The zinc alloy powder for use in the alkaline batteries may also be obtained from a zinc alloy molten metal obtained by dissolving metallic elements, i.e., indium, bismuth, and aluminum, in a zinc molten metal obtained by melting a zinc ingot (see Japanese Patent No. 3436495).
Known techniques for producing a powder by powdering the zinc alloy molten metal include a gas atomization method in which the zinc alloy molten metal is powdered by being atomized with a high pressure gas, and a centrifugal disk atomization method in which the zinc alloy molten metal is powdered by being dispersed using a high-speed rotating disk (see Japanese Patent No. 5102970).